/**
 *     Head.c -- Displays beginning (heads) of file
 *              (c) Charles Petzold, 1998
 */

#include <windows.h>

#define ID_LIST 1
#define ID_TEXT 2
#define MAXREAD 8192
#define DIRATTR (DDL_READWRITE | DDL_READONLY | DDL_HIDDEN | DDL_SYSTEM | DDL_DIRECTORY | DDL_ARCHIVE | DDL_DRIVES)
#define DTFLAGS (DT_WORDBREAK | DT_EXPANDTABS | DT_NOCLIP | DT_NOPREFIX)

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK ListProc(HWND, UINT, WPARAM, LPARAM);

WNDPROC OldList;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("head");
    HWND hwnd;
    MSG msg;
    WNDCLASS wndclass;

    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName, 
                        TEXT("head"),
                        WS_OVERLAPPEDWINDOW,
                        CW_USEDEFAULT, CW_USEDEFAULT, 
                        600, 600,
                        NULL, NULL, hInstance, NULL);
    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);

    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static BOOL bValidFile;
    static BYTE buffer[MAXREAD];
    static HWND hwndList, hwndText;
    static RECT rect;
    static TCHAR szFile[MAX_PATH + 1];
    HANDLE hFile;
    HDC hdc;
    int i, cxChar, cyChar;
    PAINTSTRUCT ps;
    TCHAR szBuffer[MAX_PATH + 1];

    switch (message)
    {
        case WM_CREATE: {
            cxChar = LOWORD(GetDialogBaseUnits());
            cyChar = HIWORD(GetDialogBaseUnits());
            rect.left = 20*cxChar;
            rect.top = 3*cyChar;
            hwndList = CreateWindow(TEXT("listbox"), NULL,
                                    WS_CHILDWINDOW | WS_VISIBLE | LBS_STANDARD,
                                    cxChar, cyChar*3,
                                    cxChar*13 + GetSystemMetrics(SM_CXVSCROLL),
                                    cyChar*10,
                                    hwnd, (HMENU)ID_LIST,
                                    (HINSTANCE)GetWindowLong(hwnd, GWLP_HINSTANCE), NULL
                                    );
            GetCurrentDirectory(MAX_PATH + 1, szBuffer);
            
            hwndText = CreateWindow(TEXT("static"), szBuffer,
                                    WS_CHILDWINDOW | WS_VISIBLE | SS_LEFT,
                                    cxChar, cyChar,cxChar*MAX_PATH, cyChar,
                                    hwnd, (HMENU)ID_TEXT,
                                    (HINSTANCE)GetWindowLong(hwnd, GWLP_HINSTANCE), NULL
                                    );
            OldList = (WNDPROC) SetWindowLong(hwndList, GWLP_WNDPROC, (LPARAM)ListProc);
            SendMessage(hwndList, LB_DIR, DIRATTR, (LPARAM)TEXT("*.*"));
            return 0;
        }
        case WM_SIZE: {
            rect.right = LOWORD(lParam);
            rect.bottom = HIWORD(lParam);
            return 0;
        }
        case WM_SETFOCUS: {
            SetFocus(hwndList);
            return 0;
        }
        case WM_COMMAND: {
            if(LOWORD(wParam) == ID_LIST && HIWORD(wParam) == LBN_DBLCLK) {
                if(LB_ERR == (i=SendMessage(hwndList, LB_GETCURSEL, 0, 0))) break;
                SendMessage(hwndList, LB_GETTEXT, i, (LPARAM)szBuffer);
                if (INVALID_HANDLE_VALUE != (hFile = CreateFile(szBuffer, 
                    GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, NULL))) {
                        CloseHandle(hFile);
                        bValidFile = TRUE;
                        lstrcpy(szFile, szBuffer);
                        GetCurrentDirectory(MAX_PATH+1, szBuffer);
                        if(szBuffer[lstrlen(szBuffer)-1] != '\\')
                            lstrcat(szBuffer, TEXT("\\"));
                        SetWindowText(hwndText, lstrcat(szBuffer, szFile));
                    } else {
                        bValidFile = FALSE;
                        szBuffer[lstrlen(szBuffer)-1] = '\0';
                        // If setting the directory doesn't work, maybe it's 
                        // a drive change, so try that.
                        if (!SetCurrentDirectory(szBuffer+1)) {
                            szBuffer[3] = ':';
                            szBuffer[4] = '\0';
                            SetCurrentDirectory(szBuffer+2);
                        }
                        // Get the new directory name and fill the list box.
                        GetCurrentDirectory(MAX_PATH+1, szBuffer);
                        SetWindowText(hwndText, szBuffer);
                        SendMessage(hwndList, LB_RESETCONTENT, 0, 0);
                        SendMessage(hwndList, LB_DIR, DIRATTR, (LPARAM)TEXT("*.*"));
                    }
                    InvalidateRect(hwnd, NULL, TRUE);
            }
            return 0;
        }
        
        case WM_PAINT: {
            if (!bValidFile) break;
            if (INVALID_HANDLE_VALUE == (hFile = CreateFile(szFile, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, NULL))) {
                bValidFile = FALSE;
                break;
            }
            ReadFile(hFile, buffer, MAXREAD, (LPDWORD)&i, NULL);
            CloseHandle(hFile);
            // i now equals the number of bytes in buffer.
            // Commence getting a device contex for displaying text.
            hdc = BeginPaint(hwnd, &ps);
            SelectObject(hdc, GetStockObject(SYSTEM_FIXED_FONT));
            SetTextColor(hdc, GetSysColor(COLOR_BTNTEXT));
            SetBkColor(hdc, GetSysColor(COLOR_BTNFACE));
            // Assume the file ASCII
            DrawTextA(hdc, buffer, i, &rect, DTFLAGS);
            EndPaint(hwnd, &ps);
            return 0;
        }
       
        case WM_DESTROY: {
            PostQuitMessage(0);
            return 0;
        } 
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

LRESULT CALLBACK ListProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    if (message == WM_KEYDOWN && wParam == VK_RETURN) {
        SendMessage(GetParent(hwnd), WM_COMMAND, MAKELONG(1, LBN_DBLCLK), (LPARAM)hwnd);
    }
    return CallWindowProc(OldList, hwnd, message, wParam, lParam);
}